Phased array radar systems employ a bank of antennas, arranged in a particular orientation, each emitting a signal that is phase-adjusted to construct a radiation pattern in a desired direction. Phased arrays often use antennas having a fixed phase-relationship to generate a signal in one direction. Other phased arrays adjust the phase of each antenna to steer the beam in different directions.
Wideband radar systems are highly desirable, as they offer the increased ability to discriminate and identify a target. However, current phased arrays cannot be steered, using only phase, over wide bandwidths. This is because the phase shifters at a fixed phase will only be accurate for one frequency within the frequency spectrum transmitted. In other words, if the phase is fixed, the direction of the beam will shift over frequency and even small changes in frequency can effectively mispoint the phased array. Further, for very narrow wideband pulses, the returns across the array will not align in time and so cannot be added coherently. Ideally, wideband beam steering of phased arrays could be accomplished through time delay steering, instead of phase shifters. Instead of adjusting for phase difference, the time delay units adjust for the difference in time of arrival at each element. But time delay units are still too large and expensive to be practically implemented. Accordingly, there is a need in the art for phased-array radar that is capable of phase-only steering, at any unambiguous angle (i.e. out to the first grating lobe) for wideband signals.